Elastic suspension and resilient mounting means for magnetic systems



Nov. 8, 1949 F. c. FARNHAM 2,487,047

ELASTIC SUSPENSION AND RESILIENT MOUNTING MEANS FOR MAGNETIC SYSTEMS Filed NOV. 12, 1947 4 Sheets-Sheet 1 Nov. 8, 1949 F. c. FARNHAM 2,487,047

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ELASTIC SUSPENSION AND RESILIENT MOUNTING MEANS FOR MAGNETIC SYSTEMS A 'fron y Patented Nov. 8, 1949 Anms'rlc sUsraNsroN AND RESILIENT MOUNTING MEANS FOR MAGNETIC SYSTEMS Frank c. Farnham, Baltimore, ma.

Application November 12, 1947, Serial No. 785,410

8 Claims. (C l. 175-183) able element of a magnetic measuring instrument. i

Still another object -ot my invention ls to provide an arrangement of fiber-like suspension means forthe angularly movable magnetic element of a magnetometer including a resilient means for normally clamping the magnetic element in iixecir position when the instrument is to be transported'to a locationatwhich a magnetic survey is to befmade.

Still another object of my invention is to provide a construction of -magnetic indicating element for magnetometers, including means for counterbalancing the indicating element for predetermined adjustment thereoi with respect to a calibrated scale. f

A still further object of my invention is to provide a construction of angularly movableindicator system for magnetometers including an arrangement of counterweights 'adjustable to improve the sensitivity of the indicator system byadjusting both' elastic torque and gravitational torque.

Still another object of my invention is. to provide an improved construction of indicator mechanism for magnetometers, as set forth more fully in the specification hereinafter following by referring to the accompanying drawings, in which:

Figure 1 is a frontelevational view of a magnetometer embodying my invention; Fig. 2 is an enlarged front elevational view of the magnetometer of my invention with certain of the parts illustrated in vertical section; Fig. 3 is a vertical sectional view taken through the magnetometer and illustrating Vthe movable indicating element in clamped position therein; Fig. 4 is a view similar to the lview illustrated in Fig. 3 but illustrating the movable element of the magnetometer in released position` ready for a reading; Fig. 5 is a vertical sectional view taken on line B-Iof Fig. 4; Fig. 6 is a side elevational view of the indicating system of the magnetometer showing certain of the partsin Vertical.

section; Fig. "I is a horizontal sectional view taken on line 1-1 of Fig. 6; Fig. 8 is a perspective view ofone of the spring clamps associated with vone end of the angularly movable indicator system; Fig. 9 is a perspective view of the spring clamp which is associated with the other end oi the angularly movable indicating system in the magnetometer of my invention; and Fig. 10 is an end view of the magnetic element constituting the part of the angularly shiftable indicating mechanism employed inthe structure of my invention.

My invention is directed to the precision suspension of the magnetic indicating element of an instrument for measuring magnetic fields. I provide an elastic suspension for an angularly shiftable indicating element of a magnetometer by which the mass of the balanced system is properly distributed. The elastic suspensionis constructed of sufficient strength and practical length so that the instrument is iieldworthy. The angularly shiftable magnet element is provided with adjustable counterweights for compensating for counterclockwise gravitational torque `and. clockwise magnetic torque for increasing the sensitiveness of the indicating system. A iiber suspension means is employed for the angularly shiftable balanced magnetic-system where the suspension means is resiliently supported at opposite ends thereof. The magnetometer of my invention has been found to be very eillcient in operation.

The counterweight is so adjusted that the counterclockwise gravitational torque exerted by it is equal to the clockwise magnetic torque upon the magnetic element at a place where the vertical component of the earths magnetic eld is normal, and the iiber is adjusted so that the resultant elastic torque on the element is zero when it is horizontal.A Now, if the system is displaced clockwise through a small angle it will be subject to two turques, the elastic torque of the fiber which tends to return it to its original position and the gravitational torque on the sensitivity 5 adjustment weight which tends to displace it further. I f the elastic torque is greater than the gravitational torque, ,the system will be stable and return to its original position. Since the resultant torque tending to return the system to its undeilected position is the diii'erence between the elastic and gravitational torques, the system canv be adjusted to have as high a' sensitivity as desired by making the diierence sufciently small, this in spite of the lfact that the elastic torque may be rather large.- Although Referring to the drawings in detail, 'reference character I designates the magnetic needle which passes through the central magnetic hub-like member 2. The hub-like member 2 is frustoconically shaped on one end as represented at 3, and on the other end there are a multiplicity of flat angularly disposed plane faces represented at 4, 4a, and 4b, as shown more particularly in Fig. 10. The central, magnetic hub-like member 2 has plug members 5 and 6 screw-threaded into the apexes of the opposite ends thereof. These screw-threaded plugs 5 and 6 are each provided with eyelets 5a and 6a through which the ends of the fibers 1 and 8 are threaded and fastened. Fibers 1 and 8 are formed from elastic material 'of considerable strength andare secured at the outer ends thereof by two leaf springs represented at 8 and I 0. The leaf springs 9 and I0 are tonguelike members which extend from circular framelike portions 9a and Illa which are seated within the annular recesses II and I2 of cylindrical members Ila and I2a. The cylindrical members IIa and I2a are both centrally apertured for the passage of the ends of tubular members I4 and I5. The tubular members I4 and I5 extend into the opposite poles I6 and I1 of the U-shaped magnetic frame I8 and are screw-threaded therein to form cylindrical protective housings through which the ber thread-like members 'I and 8 extend. The ends of the pole pieces I6 and I1 are split, as represented at iGa and Ila, to impart resilience thereto and facilitate the introduction of the members I4 and I5 into the pole pieces I6 and I1.

The central hub-like member 2, which is resiliently suspended for rotary movement on the iibres 1 and 8, is arranged with relation to a pair of resilient conning arms represented at I9 and 20. The arms I9 and 20. are secured at I9a and 29a to the inner faces of the substantially parallel extending portions I6 and I1 and are each apertured as represented more clearly in Figs. 8 and 9 to conform with the shapes of the opposite ends of the hub-like member 2. That is to say, the

resilient confining arm I9 is apertured adjacent its extremity, as represented at I9b in a substantially polygonal shape to conform with the shapes of the faces 4 at one of the hub-like members 2 as represented in Fig. 8. The resilient strip 20 is shown in Fig. 9 with an aperture 20h adjacent the end thereof operative to engage the frustoconical shaped end 3 of the hub-like member 2. Thus the confining arms I9 and 2li serve to support the central magnetic hub-like member 2 while the instrument is not in use or while the instrument is being transported from place to place for protecting the delicate mechanism of the magnetometer. When the instrument is to be placed in use the conining arms i9 and 2li are spread away from opposite ends of the central magnetic hub-like member 2 for releasing the central hub-like member 2 and allowing axial movement thereof about the axis of the threadlike suspensions 1 and 8.

It will be observed that the confining arms I9 and 28 are substantially at strip-like members which occupy a minimum amount of space between the inner faces of the parallel extending portions I6 and I1 and the ends of the hub-like member 2. These coniining arms I9 and 20 have p 4 sumcient movement to engage or disengage the shaped ends of the hub-like member 2. This displacement is effected by operation of a plunger 2| having a frusto-conical head 2Ia adapted to enter the space between the resilient coniining arms I9 and 28 for displacing said arms from the position illustrated in Fig. 3 to the position illustrated in Fig. 4. This action results in a release of the ends of the magnetic hub-like member 2 which functions as an amature between the pole pieces I8 and I'I.

The U-shaped magnetic frame I8 is apertured at I 8a to permit the upward and downward movement of plunger 2|. The aperture I8a is aligned with a corresponding aperture 22 in the circular frame structure 23 which is similarly aligned with the aperture 24 in the supporting member 25. The supporting member 25 is connected through suitable attachment screws 26 with the circular frame structure 23. Aperture l24 in supporting member 25 terminates in the transverse aperture 21 extending through supporting member 24. A horizontally extending actuating member 23 extends through aperture 21 in supporting member- 25 and is revolvable under control of the manual hand grip 29 and lever 30. An eccentric portion 3i on member 28 engages the end of plunger 2I for raising or lowering the plunger 2I. The plunger is displaced from the position illustrated in Fig. 3 to the position illustrated in Fig. 4 in order to unlatch the movable armature 2 from its protective inoperative position to its operative position. Armature 2 has associated therewith the counter-balance weights constituted by adjustable nut members 32 and 33 which are movable on screw-threaded members 34 and 35 for dynamically balancing the armature 2 about the axis constituted by thread-like suspension means 1 and 8. In addition to the counterbalance thus provided, we also provide a ne adjustment mass compensating means in the form of an adjusting screw 36 adjustable diametrically through the armature 2.

The armature 2 carries the magnetic needle I which is operative within the magnetic member '31 y secured within the circular frame 23. The magnetic member 31 has a scale 38 associated therewith, the scale being suitably calibrated as represented at 39 and coacting with the indicator 40 carried by the armature 2.

The housing formed by the circular frame 23A .is completed by circular end plates 4I and 42 which are secured within the circular frame 23 by resilient ring members 43 and 44 against abutments formed by annular shoulders 23a and,23b within the circular frame 23.

The end plates 4I and 42 are both formed from transparent material in order to permit observation of the operation of the instrument. n., Plate members 4I and 42 each carry the rojecting cover members 45 and 46 respecti k ly. Cover members 45 and 46 are each remov'ble from sleeve members 45a and-46a carried byrthe plate members 4l and 42 to permit access to the resilient supports 9 and Il'for insuring proper maintenance of the apparatus in the eld.

The supporting member 25 is mounted in a trunnion-like ring device 41 connected through pins 48 and 49 with the supporting member 25 and through pins 56 and 5I with the vertically extending supports 52' and 53 mounted upon the I,

, i the adjustable tripod supporting legs l1 are adjustably connected. The tripod .frame il includes a depending frame portion Il associated therewith through which the pendulum-like depending member u extends for suspending the magnetic compass and level device I0. Suitable counter-balance means DI are associated with the magnetic compass and level I0 as represented more particularly in Fig. 1.

A thermometer 82 is positioned within the housing frame by circular frame 23 and is provided with temperature scale 62 which is readily readable through the transparent sides 4i and 42 of the housing.

The shaping of the opposite ends ofthe armature 2 to enable these ends to be gripped by the shaped ends of the resilient arms Il and 2l is an important feature of my invention. The fiber-like suspension of the armature 2 by members 1 and 8 connected to resilient means I and I0 is also of prime importance in the successful operation of the apparatus of my invention.

While I have described my invention in certain preferred embodiments I realize that modiilcations may be made and no limitations upon my invention-are intended other than may be imposed by the scope-of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

l. A magnetometer comprising a frame structure, a scale carried by said frame structure, a permanent magnet disposed within said frame structure and terminating in a pair of substantially parallel pole pieces, a tubular member carried by each of said pole pieces, an armature member arranged between said pole pieces, a thread-like suspension connected with opposite ends ,of said armature member and extending through said tubular member, resilient means carried by said frame structure for supporting the ends of said thread-like suspensions, an lndicator carried by said armature member and coacting with the scale on said frame structure and means for resiliently gripping said armature member in a fixed position against rotation.

2. A magnetometer comprising a frame structure, a scale carried by said frame structure, a permanent magnet disposed within said frame structure and terminating in a pair of substantially parallel pole pieces, a tubular member carried by each of said pole pieces, an armature member arranged between said pole pieces, a thread-like suspension connected with opposite ends of said armature member and extending through said tubular member, resilient means carried by said frame structure for supporting the ends of said thread-like suspensions, an indicator carried by said armature member and coasting with the scale on said frame structure, resilient means disposed between the ends of said armature member and said permanent magnet and operative to. normally support. said armature member against angular movement and means for displacing the aforesaid means for releasing said amature mem-ber for permitting angular movement thereof 'under control of magnetic variations.

asomar jecting axially in opposite directions from said frame structure, an armature member disposed between said pole faces, fibre-like members extending from opposite ends of said armature member through said tubular members and secured to said frame structure for suspending said armature member for angular movement, an indicator extending from saidarmature member and coacting with said scale and a magnetic needle carried by said armature member and movable in an angular path extending through said circular magnet.

Y 4. A magnetometer comprising a frame structure, a circular magnet and scale housed within said frame/` structure, a U-shaped permanent magnet extending through one side of said circular magnet into said frame structure and terminating in substantially parallel pole faces centrally of said frame structure. tubular' members supported by each of said pole faces and projecting axially in opposite directions from said frame structure, an armature member disposed between said pole faces, nbre-like members extending from opposite ends of said armature member through said tubular members and secured to said frame structure for suspending said amature member for angular movement, an indicator extending from said armature member and coacting with said scale, a magnetic needle carried by said armature member and movable in an angular path extending through said circular magnet and means fogglocking and/or unlocking said armature member Jin a fixed or freely;y movable suspended positiqnbetween said pole faces.

5. A magnetom'eter comprising a frame structure, a circular magnet and scale housed within said frame structure. a U-shaped permanent magnet extending through one side of said circular magnet into said frame structure and terminating in substantially parallel pole faces centrally of said frame structure, tubular members supported by each of said pole faces and projecting axially in opposite directions from said frame structure, an armature member disposed between said pole faces, nbre-like members extending from opposite ends of said armature member through said tubular members and secured to said frame structure` for suspending said amature member for angular movement, an indicator extending from said armature member and coacting with said scale, a magnetic needle carried by said armature member and movable in an angular path extending through said circular magnet and means carried by said frame structure for enclosing said tubular members and the connections of said fibre-like members with said frame structure f 6. In a magnetometer, a magnetic frame structure terminating in a'pair of spaced substantially parallel pole faces, tubular members projecting from each of said pole faces, a magnetic armature member having a frusto-conical terminus at one end and a polygonally shaped terminus at the other end, nbre-like members connected with opposite ends of said armature and extending through said tubular members and resiliently secured to said frame structure and mans disposed between said pole faces and the ends of said armature member for resiliently'engaging or disengaging the frusto-conically and. polygonally shaped termini of said armature member.

7. In a magnetometer, a magnetic frame structure terminating in a pair of spaced substantially parallel pole faces, tubular members projecting from each of said pole faces, a magnetic armature member having a frusta-conical terminus aaazosv member and means for controlling the position of said resilient strip members to etl'ect an engagement or disengagement of said strip members with the termini ot said amature member for locking or unlocking said armature member l with respect to said pole faces.

8. Ina magnetometer, a magnetic frame structure terminating in a pair of spaced substantially parallel pole faces, tubular member projecting from each of said pole faces, a magnetic armature member having a frusto-conical terminus at one end and a polygonally shaped terminus at the other end, libre-like lmembers connected with opposite ends of said armature and extending through said tubular members and resiliently secured to said frame structure, a resilient strip member individual to each of said pole faces, one

8 oi said resilient strips having a circular aperture therein operative to engage the irusto-conically shaped terminus of said armature and the other of said resilient strips having a polysonally shaped aperture therein operative to engage the polygonally shaped terminus of said armature member. means for controlling the position oi' vsaid resilient strip members to eirect an engagement or disengagement of said strip members with the termini of said armature member for locking or unlocking said armature member with respect to said pole faces and adjustable means extending from said armature member for counterbalancing the angular mature member.

` FRANK c. FARNHAM.

REFERI'IISTCI'ISv CITED The following references are of record in the ille of this parten-t: y- UNrrED STATES PATENTS Number Name Date 1,701,603 Bauer et al. Feb. 12, 1929 1,202,868I Hotchkiss et al Feb. 19, 1929 v 1,909,619 Herrick May 16, 1933 2,010,245 Roux Aug. 6, 1935 2,362,616 Cloud Nov. 14, 1944 movement of said ar- 

